I guess that again, this is one of those situations where no matter what you say, someone will be offended and not take it the way it was intended. The example Shores gave where I asked them to please take the conversation to a PM, someone could have been offended by that request. Someone is going to be offended by offering bean dip, or changing the subject like in the dog example. It's inevitable. I don't think that we're all going to be able to agree on the right way to do this.
I do report threads to the mods when they get out of control. The mods are great, but they have lives too, and aren't always able to address the situation immediately. Going back to the OP's suggestion of just not reading the thread, that's fine if it's clear that the thread is going to be a hot topic. But when the conversation was about Kanye West, Big Brother, eating out of a jar, etc., these are conversations that I want to participate in, and were going fine until someone comes along and creates drama.
As a member of this forum, I think that it's fine to interject and ask people if they would mind breaking it up so that we can go back to the conversation, and to do that in whatever way they feel comfortable, as long as it's not intended to be rude or snarky.